Revascularization with laser outputs

ABSTRACT

Apparatus for treating a patient&#39;s heart by stimulating revascularization of the heart or creating channels in the heart. The apparatus includes a catheter, a laser energy source coupled to the catheter, and a control circuit. The control circuit is configured to cause the laser energy source to deliver an output of laser energy over a first time period shorter than a heart beat cycle.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation in part application of U.S. patentapplication entitled REVASCULARIZATION WITH HEART PACING, applicationSer. No. 08/793,000, Filed on Feb. 3, 1997, inventors: Murphy-Chutorian,Mueller.

The following applications are hereby incorporated herein by reference:U.S. patent application Ser. No. 08/852,977 Entitled ULTRASOUND DEVICEFOR AXIAL RANGING, Inventor(s): Zanelli, et. al. U.S. patent applicationEntitled METHOD AND APPARATUS FOR CREATION OF DRUG DELIVERY AND/ORSTIMULATION POCKETS IN THE MYOCARDIUM, application Ser. No. 08/773,778,Filed on Dec. 23, 1996, inventor(s): Mueller; U.S. patent applicationEntitled METHOD AND APPARATUS FOR MECHANICAL TRANSMYOCARDIALREVASCULARIZATION OF THE HEART, U.S. Pat. No. 5,871,495, Filed on Sep.13, 1996, inventor(s): Mueller; U.S. patent application Entitled METHODFOR NON-SYNCHRONOUS LASER ASSISTED TRANSMYOCARDIAL REVASCULARIZATION,U.S. Pat. No. 5,785,702, filed on Oct. 15, 1996, inventor(s):Murphy-Chutorian; and U.S. Patent Application Entitled MINIMALLYINVASIVE METHOD FOR FORMING REVASCULARIZATION CHANNELS, Application No.08/794,733, inventor(s) Daniel et. al.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to a method and apparatus forrevascularization of a heart, and more particularly to a method andapparatus for revascularization using laser outputs.

2. Description of Related Art

Heart disease is a significant health problem which has been the subjectof substantial medical study. By-pass surgery has become commonplace,yet such surgery may only partially correct a diminished blood supply toheart muscle and may be unavailable to many patients, either because ofthe nature of the occlusions or the physical condition of the patient.

One promising alternative or adjunctive technique for treating suchcases is known as transmyocardial revascularization (TMR). Thistechnique was considered in the work of Dr. C. Beck in "the Developmentof a New Blood Supply to the Heart by Operation," Annals of SurgeryAnnals of Surgery, Vol. 102, No. 5 (11/35) pp. 801-813. The method wasalso studied in the work of Dr. M. Mirhoseini and M. Cayton, an exampleof which is found in "Lasers and Cardiothoracic Surgery" in Lasers inGeneral Surgery (Williams and Williams, 1989) pp. 216-223. A device toperform TMR is described in Aita et al., U.S. Pat. No. 5,380,316, issuedJan. 10, 1995. In TMR generally the surgeon creates narrow channels inthe heart at the surface of a ventricle of the heart. The surgeongenerally uses a laser to create these channels either by accessing theendocardium through a percutaneous route or the epicardium through anincision in the chest wall. The pressure within the left ventricleduring systole forces oxygenated blood into the channels andconsequently oxygenates the ischemic myocardium of the left ventricle.

It is desirable to be able to control the time point within the cycle ofheartbeats at which the heart is revascularized. A heart synchronizedpulse laser system which operates on a beating heart between the R and Twaves of the electrocardiogram (ECG) signal is described in U.S. Pat.No. 5,125,926 (Rudko).

An electrocardiogram signal may not always provide the most accurateindication of heart function. Further, the electrocardiogram signal is apassive indication of heart rate. It is not a method to control the rateat which the heart beats.

There is a need for an apparatus for stimulating revascularization ofthe heart or creating channels in the heart where the revascularizationevent caused by the revascularization device can occur at a selectedtime in relation to the heartbeat. There is a further need for anapparatus for treating a heart by stimulating revascularization of theheart or creating channels in the heart where the device can control theheartbeat rate. There is further need to reduce the number of cyclesover which a laser must be fired to achieve the desired depth ofchannels in the heart.

SUMMARY OF THE INVENTION

Accordingly, an object of the invention is to provide an apparatus forstimulating revascularization of the beating heart or creating channelsin the heart.

Further, an object of the invention is to provide an apparatus forstimulating revascularization of the heart or creating channels in theheart where the revascularization or creation of channels occurs at atime when the heart is less sensitive to external influences.

Another object of the invention is to provide an apparatus forstimulating revascularization of the heart or creating channels in thebeating heart where the revascularization or creation of channels occurswhen the beating heart is relatively still.

A further object is to reduce the number of cycles over which the lasermust be fired.

Another object of the invention is to provide an apparatus forstimulating revascularization of the heart or creating channels in theheart where the revascularization event caused by the revascularizationdevice can occur at a selected time in relation to the heartbeat.

Another object of the invention is to provide an apparatus for treatinga heart by stimulating revascularization of the heart or creatingchannels in the heart where the device can control the heartbeat rate.

These and other objects are achieved in an apparatus for treating apatient's heart by stimulating revascularization of the heart orcreating channels in the heart. In one embodiment the apparatus includesa catheter, a laser energy source coupled to the catheter, and a controlcircuit. The control circuit is configured to cause the laser energysource to deliver an output of laser energy over a first time periodshorter than a heart beat cycle.

In one embodiment, the set of laser pulses comprises a number of laserpulses sufficient to cause one heartbeat per set of laser pulses. In oneembodiment the set of laser pulses comprises a number of laser pulses tocause no more than one heartbeat per set of laser pulses.

Embodiments of the invention include methods of revascularization and acomputer program product for revascularization.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a block diagram of a system for performing transmyocardialrevascularization.

FIG. 2 is a block diagram of a system for performing transmyocardialrevascularization including a block diagram of a pulse generator.

FIG. 3a is a timing diagram for revascularization with heart pacingincluding a foot switch signal.

FIG. 3b is a timing diagram for revascularization with heart pacing.

FIG. 3c is a timing diagram for revascularization with heart pacing.

FIG. 3d is a timing diagram for revascularization with heart pacingincluding laser pulses that cause heartbeats.

FIG. 3e is a timing diagram for revascularization with heart pacingincluding laser pulses that cause heartbeats and including multiplelaser pulses per heartbeat.

FIG. 3f is a timing diagram for revascularization with heart pacingincluding multiple laser pulses per heartbeat.

FIG. 3g is a timing diagram for revascularization with heart pacingincluding multiple laser pulses of different intensities.

FIG. 4a is a perspective view of a fiber optic catheter with pacingleads.

FIG. 4b is a perspective view of a fiber optic laser energy deliverydevice handpiece with pacing leads.

FIG. 4c is a perspective view of a piercer with an electrode.

FIG. 4d is a cross sectional view of an electrically controllablemechanical cutter.

FIG. 5a is a cross sectional view of a catheter with fiber optic fibers.

FIG. 5b is a cross sectional view of a catheter with fiber optic fibers.

FIG. 5c is a cross sectional view of a catheter with fiber optic fibers.

FIG. 5d is a cross sectional view of a catheter with fiber optic fibers.

FIG. 6 is a cross sectional view of a heart with revascularizationchannels created in a percutaneous procedure.

FIG. 7 is a cross sectional view of a heart with a revascularizationchannel created in a surgical procedure.

FIG. 8a is a view of channels and pockets created in heart tissue.

FIG. 8b is a view of multiple legs created from channels in hearttissue.

FIG. 9 shows a system with a computer program for laserrevascularization.

FIG. 10 is a flow chart showing a program for revascularization withlaser revascularization.

FIG. 11 is a timing diagram showing laser outputs.

FIGS. 12a-12d are timing diagrams showing laser outputs and heart waves.

FIG. 13 is a flow chart showing a program for revascularization withsensor verify.

FIG. 14 is a flow chart showing a program for revascularization withsensor verify and pace rate calculation.

DETAILED DESCRIPTION

The apparatus and method of the present invention create channels orstimulation zones or both in the heart through a series ofrevascularization events. A revascularization device is used to createchannels or stimulation zones in the heart. A revascularization deviceis one or more laser energy delivery devices (fired alone,simultaneously, or sequentially), a mechanical cutter, an ultrasoundenergy delivery device, or other device or devices for creating channelsin heart tissue. A revascularization event is an action of therevascularization device as the device cuts, burns, lases, or otherwisecreates or lengthens channels in the heart tissue. The channels orstimulation zones allow for improved bloodflow in heart tissue and/orhelp to stimulate regrowth of capillaries.

In an embodiment of the invention, revascularization energy is deliveredto the heart in the form of an output of laser energy. An output oflaser energy may include multiple laser pulses delivered during a timeperiod generally not greater than a heart beat cycle. An output may alsoinclude a continuous wave of laser energy. The burst may create a singleheart beat.

In another embodiment of the invention, heart function is sensed afterenergy is delivered to the heart to cause the heart to beat. If aheartbeat is not detected, then the operator is notified. If a heartbeatis detected, a revascularization event is delivered to the heart.

Embodiments of the present invention provide revascularization events tothe heart at a specific time in the heartbeat cycle. In some embodimentsof the invention the heart is paced. A pace signal starts a heartbeatcycle. A revascularization event is provided to the heart relative tothe pace signal. By timing the revascularization event with respect tothe pace signal, the revascularization event is provided at a selectedtime within the created heartbeat cycle.

The time within the cycle between the two created heartbeats at whichthe revascularization event occurs can be selected to provide an optimaltime at which to cause a revascularization event to occur. The timedelay can be selected so that the revascularization occurs when theheart is less sensitive to external stimuli, or when the heart is morequiet so as to reduce the risk to the patient and help achieve betterrevascularization. After the created heartbeat is created, arevascularization period begins and during the revascularization perioda revascularization event is caused to occur.

An energy source, including but not limited to a pacemaker, is used topace the heart and cause the heart to beat at a selected rate. Thesurgeon may enable the revascularization apparatus with a foot switch. Acontrol circuit receives input from the surgeon's foot switch. Thecontrol circuit causes the revascularization device to start arevascularization event at a time relative to the time the energy sourcecauses the heart to beat. Among the advantages of pacing the heart whileperforming revascularization is that the surgeon can control the rate ofthe heart and not have to rely exclusively on the natural rhythms of apossibly compromised or sick heart.

Referring now to FIG. 1, the surgeon enables the apparatus throughfootswitch 22. Pace control block 20 receives a signal from safetyinterlocks 23 and footswitch 22, which is operated by the surgeon. Pacecontrol block 20 outputs signals to pacing leads 24 which provide apacing signal to patient 26. The pacing signal causes a createdheartbeat and causes the patient's heart to beat at the pace rateprovided by pace control block 20. Pace control block 20 sends a signalto a laser 28 to cause laser 28 to provide laser energy through opticalfiber 30 to the patient's heart at a selected time in relation to thecreated heartbeat. The energy provided through optical fiber 30 is usedto revascularize or to create channels in the heart of patient 26.

Referring now to FIG. 2, pace control block 20 includes microcomputerbased timing controller 40, pulse generator 38, and laser controller 42.Desired rate 34 is coupled to a microcomputer based timing controller 40and controls the rate at which pulse generator 38 provides pacingsignals to patient 26 via pacing leads 24. Desired current 36 is coupledto pulse generator 38 and controls the level of current that is providedto patient via pacing leads 24 in order to pace the patient's heart. Theoutput of microcomputer based timing controller 40 provides timingsignals to laser controller 42. The timing signals cause therevascularization event to occur at the selected time relative to thecreated heartbeat created by pulse generator 38. The input of sensor 32is coupled to patient 26. Sensor 32 is not necessary for the operationof the system and is therefore optional. The optional signal from sensor32 is a heartbeat indicator signal. The heartbeat indicator signalindicates whether the patient's heart is beating. The output offootswitch 22, safety interlocks 23, timing signals from microcomputerbased timing controller 40, and the output of sensor 32 are combined inlaser controller 42 to provide a laser active signal to laser 28. Thus,a signal is provided only when all of the following occur: the surgeonhas enabled the system via the footswitch, the safety interlocks areenabled, the optional heartbeat indicator indicates that the heart isbeating, and a signal is provided to fire the laser from the output ofmicrocomputer based timing controller 40. Laser 28 provides laser energyover optical fiber 30 in order to create a revascularization event inthe heart to stimulate revascularization of the heart of patient 26 orto create channels in the heart to improve blood flow.

In an alternative embodiment signals from foot switch 22 or from sensor32 or both could be input into microcomputer based timing controller 40instead of into laser controller 42. In such a configuration,microcomputer based timing controller 40 would then provide appropriatesignals to laser controller 42 partially in response to signals fromfoot switch 22 or from sensor 32. Also, instead of providing control topulse generator 38, microcomputer based timing controller 40 couldreceive information from pulse generator 38 regarding the timing ofpulses and then microcomputer based timing controller 40 would providecontrol to laser controller 42 in response to the timing of pulses.Microcomputer based timing controller 40 is a microcomputer that runs aset of software instructions recorded in a memory. Alternatively,integrated circuit logic may be used to perform the function ofmicrocomputer based timing controller 40.

Pulse generator 38 provides the pacing signal to the patient's heart orto another location on the patients body in order to pace the patient'sheart via pacing leads 24. Pulse generator 38 may be a heart pacemakersuch a modified model 540 External Pulse Generator, SeaMED Corp.,Redmond, Wash. The pacemaker is modified such that it generates a pulseto the pacing leads when it receives an external logic signal.Alternatively, pulse generator 38 is any artificial energy sourcecapable of causing the heart to beat. For example, the samerevascularization device used to create channels, such as a laser, maybe used to pace the heart as channels are created by timing therevascularization events to match the natural heart rate or tosynchronize with the heart rate. In such a case where a laser or otherrevascularization device is used to pace the heart, the artificialenergy source and the revascularization are the same device.

The pace rate is determined by desired rate 34 and can be set by theoperator. The rate of pace unit 38 is optimally set to a rate fasterthan the normal heartbeat rate. Heartbeat rate can be determinedmanually or by sensor 32 or by any other method or heartbeat ratemeasurement. If the signal from sensor 32 is provided to microcomputerbased timing controller 40, then controller 40 optionally uses theoutput information from the sensor 32 to determine the patient's heartrate before the patient's heart is paced and optionally calculates andapplies a pace rate faster than the unpaced heartbeat rate. Ifmicrocomputer based timing controller 40 is configured to automaticallydeliver a pace rate faster than the unpaced heartbeat rate, theautomatically determined pace rate can be manually overridden by theoperator. Sensor 32 can be an electrocardiogram unit, a pressuretransducer, a Doppler effect heartbeat rate sensor, or other sensor tomeasure heart function.

In a preferred embodiment laser 28 is a holmium laser available as anEclipse 40001 holmium laser from Eclipse Surgical Technologies, Inc.,Sunnyvale, Calif. Other types of medical lasers may also be used, forexample, an excimer laser, a CO. laser, an Argon laser, a Nd-yag laser,an erbium laser, or a diode laser. A medical laser having a wavelengthin the range of 308 milimeters to 10.6 micrometers may be used. A singlelaser may be used, or multiple lasers or multiple fibers from a singlelaser can be used in order to cause more revascularization to occur atone time. For a discussion of tuning of a laser for revascularization,see U.S. Patent Application entitled Method for Non-Synchronous LaserAssisted Transmyocardial Revascularization, Application No. 08/729325,filed on Oct. 15, 1996, which is incorporated herein by reference. As analternative to a laser revascularization device, anotherrevascularization device such as a mechanical cutter or an ultrasoundenergy delivery device may be used in order to create channels in theheart or to revascularize the heart. The revascularization device can becoupled to a catheter for percutaneous and minimally invasive surgery(MIS) approaches. Alternatively, the revascularization device can beused directly in open heart surgery. If the revascularization device iscoupled to a catheter, it can be introduced percutaneously and movedinto the heart through the vasculature.

Microcomputer based timing controller 40 can be configured so that thetime delay from the pace signal created by the pulse generator 38 to thetime of the revascularization event is a fixed time. A 120 ms delay isgenerated as a default. Alternatively, the microcomputer based timingcontroller 40 can be configured so that the time delay from the signalfrom the pulse generator 38 to the revascularization event is a variabletime. The revascularization time may be variable so that it is shorterwhen revascularization is taking place closer to the sinus node andlonger when revascularization is taking place further away. The varyingdelay may be controlled as set by the operator or automatically varied.The time delay can be set to cause the revascularization event to occurat a chosen point within the created heartbeat cycle. This chosen pointin time can be chosen so as to cause the least amount of interference orirritation to the heart. The point in time may be chosen to be the pointat which the heart is relatively quiet electrically. This point may alsobe chosen to be the point at which the heart is mechanically still. Inparticular, the revascularization event may be caused to occur after adepolarization of the heart and before a repolarization of the heart.The revascularization event may be caused to occur after an R wave andbefore a T wave produced by the heart. Microprocessor based timingcontroller 40 can be configured to have a fixed or variable number ofpulses, and variable or fixed pulse repetitive interval. Microcomputerbased timing controller 40 controls the frequency and duration of laseroutputs and the resulting revascularization events and thus has aneffect on the amount of revascularization or on the depth of the channelcreated in the heart during the revascularization event.

In an alternative embodiment, microcomputer based timing controller 40is configured to cause laser 28 to deliver multiple laser pulses foreach pace signal which are used to help create a greater depth ofrevascularization per heartbeat or to create a series of stimulationpockets connected by narrow channels. If multiple lasers or multiplefibers from one laser are used, then multiple channels can also becreated simultaneously. In another embodiment, microcomputer basedtiming controller 40 can be configured to cause laser 28 to deliverrevascularization events to the patient's heart at a time in theheartbeat cycle so that the revascularization event also causes aheartbeat. After a beat is created by a laser pulse, another laser pulseis delivered to create a revascularization event. In this mode ofoperation when footswitch 22 is activated, the pulse generator 38 isdisabled and one or more revascularization events are delivered topatient's 26 heart during a time that the pacemaker signal would havebeen delivered. In this manner the laser can be used to pace thepatients heart.

Optical fiber 30 may be introduced into patient 26 via a catheter in apercutaneous procedure. Alternatively, optical fiber 30 can be providedto patient 26 through open heart surgery or MIS techniques. A laserenergy delivery device provides the energy from the laser 28 to theheart of patient 26. In FIG. 2 the laser energy delivery device is shownas an optical fiber. Other forms of laser energy delivery devices couldalso be used to provide energy from a laser to the heart of patient 26.

FIG. 3a includes pace signal 46a, footswitch signal 50a, and a laserburst signal 54a. Signal 55a occurs after pace signal 46a is active at47a. Thus, a revascularization occurs after the heart is paced. Asshown, laser bursts 55a and 55a' occur only when foot switch signal 50ais active. Laser burst signals 55a and 55a' occur after pace signal 47abut before pace signal 47a'. Laser burst signals 55a " and 55a"' occurafter the pace signal 47a'.

By selecting the time delay between a pace signal 47a and arevascularization event 54a, the revascularization event can be causedto occur at a selected time relative to the heartbeat. This time isselected in order to reduce the possible negative effects on the heartbecause of irritation from the revascularization event such as causingarrhythmias or other disturbance to the heart. In one embodiment therevascularization event occurs when the heart is electrically quiet orwhen the heart is more still mechanically than at other times relativeto the heartbeat. Footswitch signal 50a is a signal that is provided bythe footswitch controlled by the surgeon. The time delay from the pacesignal 47a to the revascularization event 55a can be set at a fixedvalue as optimally chosen to reduce problems with the heart.Alternatively, this time delay can be variable.

As shown in FIG. 3b, the time delay between the pace signal 47b andlaser burst signal 55b is set so that the laser burst signal 55b occursafter the QRS complex 57b and the T wave 57b'. The electrocardiogramsignal 57b is shown for illustrative purposes and is not used to controlthe time at which the laser burst occurs. The heart is paced at a ratefaster than the unpaced heartbeat rate. As shown on signal 56b, the timebetween heartbeats is greater prior to signal 47b than after signal 47b.The rate of the paced heart is faster than the rate of the unpaced heartin order to allow the pace signal 46b to control the heart. The signalfrom an electrocardiogram or other sensor can be used to calculate apace rate faster than the normal unpaced heart rate and provide the pacesignal 46b at this pace rate. If the heart during revascularization goesinto a fast or chaotic rhythm the operator may change the rate of pacingin order to attempt to regulate the heart rate and return the heart rateto a rate closer to the normal heart rate.

FIG. 3c includes electrocardiogram signal 56c, pace signal 46c, andlaser burst signal 54c. Electrocardiogram signal 56c is not used tocontrol the laser burst. As can be seen in the FIG. 3c, the heart beatsin response to pace signal 46c as seen in electrocardiogram signal 56cwhich indicates heartbeats. The time delay between pace signal 47c andlaser burst signal 55c is such that the laser burst occurs during theheartbeat as represented by signal 57c. Alternatively, the laser burstcan be timed to occur simultaneously or substantially simultaneouslywith the pacing signal 47c.

FIG. 3d is a timing diagram for revascularization with heart pacingincluding laser pulses that cause heartbeats. Electrocardiogram signal56d is not used to control the laser burst or the periods at which theyoccur. As seen in the FIG. 3d, the heart rate before pace signal 47d isslower than the heart rate after pace signal 47d. Between the pacesignal 47d and 47d' the heart beats in response to the laser bursts 55d,55d', 55d", and 55d"'. As shown in FIG. 3d the revascularization eventsor the laser bursts occur at a time at which they cause the heart tobeat.

FIG. 3e includes electrocardiogram signal 56e, pace signal 46e, andlaser burst signal 54e. There are no signals from the pacer betweensignal 47e and 47e'. Laser 28 is used to pace the heart during thisperiod. Further, multiple pulses of the laser occur for each heartbeat.For example, after the laser pulse 55e which causes the heart to beat asdemonstrated by electrocardiogram signal 57e", a second laser pulseoccurs at signal 55e', which does not cause the heart to beat inresponse.

FIG. 3f illustrates revascularization with heart pacing includingmultiple laser pulses per heartbeat cycle. FIG. 3f includeselectrocardiogram signal 56f, pace signal 46f, and laser burst signal54f. Electrocardiogram signal 56f or signal from another type of sensor(e.g. pressure sensor) can be used to observe whether the heart isbeating efficiently and to disable the laser if the heart is notbeating. Laser bursts 55f and 55f' occur after pace signal 47f and afterR wave 57f and before T wave 57f'. Multiple laser bursts 55f and 55f'are provided in order to allow for possibly greater depth ofrevascularization per heartbeat cycle or to create stimulation zoneswith or without connecting channels. The rate at which the heart ispaced is faster than the unpaced rate of the heart. As seen in FIG. 3f;the time between heartbeat signals on the electrocardiogram signal 56fis greater before first pace signal 47f than the time between heartbeatsignals after pace signal 47f. It may be desirable to cause arevascularization event to occur after a depolarization of the heart andbefore a repolarization of the heart.

As shown in FIG. 3g, first pulse 55g is stronger than subsequent pulses55g, 55g', 55g", and 55g"' in order to allow the first pulse to pace theheart and subsequent pulses to be used to revascularize or create achannel into the heart. The heart beats in response to first laser pulse55g. Alternatively, first laser pulse 55g can be smaller than thesubsequent ones so that the first pulse is large enough to pace andsubsequent ones are larger for greater revascularization.

The apparatus and method described above may be used in a percutaneousprocedure, in a minimally evasive surgery (MIS) procedure, or othersurgical procedure. In a percutaneous procedure, a catheter isintroduced into the vasculature and revascularization events are createdusing the catheter. In a MIS procedure, apparatus to performrevascularization is introduced into the body through a port, an openingthat is small relative to the opening used in typical heart surgery.Other surgical methods can be used with paced revascularizationdescribed.

As illustrated in FIG. 4a electrode 62a and electrode 62b are mounted oncatheter 60 near the distal end of catheter 60. Fiber optic fibers 63are located in the interior of catheter 60 and extend to the distal endthereof in order to provide laser energy to the heart for creatingchannels and revascularization. Electrodes 62a and 62b provideartificial energy that causes a created heartbeat in the heart. Thisartificial energy is a pacing signal. Electrodes 62a and 62b are locatednear the distal end of catheter 60 in order to provide a pacing signalclose to the location of revascularization. Catheter 60 can be used forventricular pacing and artrial pacing by placing the electrodes 62a and62b on a location and on catheter 60 so that they are in either theatrium or ventricle as chosen. Electrodes 62a and 62b can be used topace directly into those locations of the heart. A sensor such as apressure transducer can also be coupled to the catheter 60 along withthe pacing electrodes 62a and 62b.

FIG. 4b is a perspective view of a fiber optic laser energy deliverydevice handpiece 62 with pacing leads as could be used for surgicalpaced revascularization or, with modifications, in MIS applications.Handpiece 62 is for controllably advancing a fiber. Such a handpiece isavailable under the name Sologrip i' from Eclipse Surgical Technologies,Sunnyvale, Calif. FIG. 4b shows electrode end 64c, electrode 64e,electrode 64d, and fiber optic fibers 65. The electrode 64d andelectrode 64e are located at the distal end of the laser energy deliverydevice handpiece 62 and extend though the laser energy delivery devicehandpiece 62. The location of the electrodes 64d and 64e provides thepacing signal close to the location of revascularization.

FIG. 4c shows a perspective view of a piercer 66 with an electrode 68.Electrode 68 is located at the distal end of piercer 66, and insulator70 is located around the distal end of the piercer 66. The piercer canbe used for revascularization. Piercer 66 may be a hollow needle,thereby allowing the laser fiber optic device to extend therethrough.Alternatively, piercer 66 may be angled fibers. Piercing, particularlywhen performing TMR from the epicardial surface is helpful to reduceacute bleeding, to anchor the device to the beating heart, and to reduceadhesions between the epicardium and the pericardium.

FIG. 4d is a cross sectional view of an electrically controllablemechanical cutter. The mechanical cutter includes a piercer 72, a spring74, and a solenoid 76. Piercer 72 is driven by spring 74 as controlledelectrically by solenoid 76. This construction allows this mechanicalpiercer 72 to be electronically controlled. The time of the piercing canbe set relative to the pace signal of the heart. Alternatively, thepiercing can be timed so as to cause the heart to beat.

Referring now to FIGS. 5a to 5d, embodiments of a catheter with fiberoptics 86 are illustrated. The FIGS. 5a to 5d show fiber bundles;however, it is appreciated that single fibers, waveguides, lenses usedwith fibers, or lenses in articulated arms could also be used. In FIG.5a the fibers 86 are surrounded by handle 80. A slot 82 is configured toreceive a control knob. FIG. 5b shows a handle 80' and a slot 84 throughhandle 80'. Slot 84 may be used for a control knob or control block toslide fibers 86 through the body of handle 80. FIG. 5c shows glassfibers 86 in a bundle of fibers. Alternatively, a single fiber, waveguide, or CO₂ laser handpiece may be used. FIG. 5d shows a protectivesheath 90 over a bundle of fibers including fibers 86. A marker 88 ispositioned around fibers 86. Marker 88 is comprised of tantalum orsimilar material. Epoxy 92 holds fibers 86 together.

In each of the paced revascularization procedures (percutaneous, MIS,and other surgical procedures), any pacemaker lead placement method canbe used. For example, pacemaker leads may be placed on a catheter, asdescribed above. A pacing lead can be introduced percutaneously byintroducing pacing leads into the p. saphenous vein and through theright femoral vein (medial to the right femoral artery), then threadingthe lead up through the inferior vena cava and into the right ventricle,and letting the lead lay on the right ventricle during the procedure. Apacing lead may be attached directly to the heart during surgery. Apacing lead can be introduced in a MIS approach wherein the pacing wireis placed directly on the epicardium through a port and is attached tothe right ventricle with a small suture needle during the procedure. Asindicated above, as with the other approaches to introducing pacingleads, the MIS approach of pacing lead placement can also be used withany of the paced revascularization procedures.

As shown in FIG. 6, paced revascularization can be performedpercutaneously. A revascularization device 94 is introducedpercutaneously into the vasculature and moved into the heart 98.Revascularization device 94 is used to create channels 108', 108", and108"' in heart 98. Here the channels are shown in the left ventricle108. The revascularization channels 108', 108", and 108"' help toimprove blood flow to the heart and help to stimulate the regrowth ofcapillaries. Channels extend from the ventricle partway through themyocardium.

FIG. 7 shows surgical paced revascularization. Laser energy deliverydevice 132 is introduced surgically into the body and creates channel130 through the epicardium 128. Minimally invasive surgery (MIS) canalso be used for paced revascularization and can be used to create achannel 130 in the epicardium 128. Pacing leads may be placedapproximately at point 134 on heart 98. Alternatively, any other methodof pacing lead placement can be used, such as placing leads in theventricle of the heart or on the laser energy delivery device 132.

As shown in FIG. 8a, narrow stimulation zones created as narrow channels112, 112', and 112" can be produced in heart tissue. Narrow channels112, 112', and 112" can be created between created pockets 114, 114',and 114" in heart tissue. Narrow channels may close and pockets mayremain open. As shown in FIG. 8b, channels may also have multiple legs114 and 114' extending from a single entry 116. FIG. 8b also shows legs118 and 118' extending from entry 120. Multiple legs 122 and 122' mayextend from a pocket 124, which is created from a single entry 126. Someof the legs may not extend through the myocardium. Such legs that do notextend through the myocardium can be referred to as blind channels andcan be used for depositing drugs directly into heart tissue.

FIG. 9 shows a system with a computer program for a laserrevascularization. In FIG. 9 laser energy source 130 is coupled toshutter 132, which shutters energy to ensure that the laser energy iswithin preset limits before laser energy is delivered through catheter150. Control computer 134 is coupled to laser energy source 130 forcontrolling the rate of firing of laser energy source. Control computer134 is coupled to shutter 132 for controlling the rate and timing ofshutter.

Operator control panel 144 includes a rate setting 146 and an outputlength setting 148. An operator can input a rate via a rate setting 146to control the number of outputs per time period. The operator can inputthe length of an output via the output length setting 148. Operatorcontrol panel 144 is coupled to control computer 134 and provides burstrate and output length to control computer 134 as selected by theoperator.

Control computer 134 includes rate, output length, and shutter computerprogram 136. Rate, output length, and shutter computer program 136controls the rate, output length, and shutter setting for laser energysource 130 and shutter 132. Rate, output length, and shutter computerprogram 136 includes rate code 138, output length code 140, and shuttercontrol code 142. Rate code 138 controls the number of outputs per timeperiod. Output length code 140 controls the length of an output. Shuttercontrol code 142 causes shutter 132 to block laser energy from laserenergy source 130 in order to ensure that laser energy from laser source130 is within preset limits. Control computer may be implemented as apersonal computer running a program recorded on a computer readablemedium such as a floppy disk, a hard disk, a ROM, an EPROM, anapplication specific integrated circuit (ASIC), a RAM, a compact disc,or any other medium or circuit capable of storage logic or instructions.Foot switch 22 is coupled to control computer 134 and allows operator toactivate laser energy source 130 under control of control computer 134.

FIG. 10 is a flow chart showing a program for revascularization withmulti pulse revascularization. A rate is received from the operator(block 220). Next, output length is received from the operator (block222). If laser has not been enabled by the operator (block 224), thenprogram returns to block 220. If laser has been enabled by operator(block 224), program shutters laser and fires (block 226). Laser isshuttered in order to allow laser to ensure laser source 130 is withinpreset limits. Next, laser is fired for an output length as requested bythe operator (block 228). Laser continues to fire outputs comprisingsets of pulses at a rate requested by the operator (block 230). Theprogram continues to cycle and returns to block 224 and laser continuesto produce outputs as long as laser is enabled by operator.

FIG. 11 is a timing diagram showing laser outputs. FIG. 11 shows atleast one heart beat cycle 164. In FIG. 11, heart beat cycle 164 is onesecond long. FIG. 11 also shows at least one laser output 162 on trace160. Laser output 162 comprises a set of pulses delivered over a periodof time that is generally not longer than the heart beat cycle 164.Shutter trace 166 shows the action of shutter to allow only the last twolaser pulses within laser output to pass to the catheter and cause arevascularization in the heart. Laser output 162 includes laser pulsesthat are spaced by 67 milliseconds. Alternatively, laser output maycomprise a continuous wave of laser energy in the shape of a smooth waveor other shaped wave. Two laser pulses may be delivered per output, or,alternatively, a set of pulses in the range of 1 to 4 may be deliveredper output.

Laser output 162 is shorter than the period of time from Q wave to a Twave of a heart before revascularization. A rest period is providedbetween laser outputs. The rest period is slightly shorter than the timeperiod from a T wave to a Q wave of the heart before revascularization.

FIG. 12a-12d are timing diagrams showing laser outputs and heart wavesin an experiment with a canine subject. ECG signals are represented bythe traces 170, 180, 200, and 210. An R-wave detect signal is shown astraces 172, 182, 202, and 212. In these figures the R-wave detect wasnot connected to the subject. A pacemaker signal is shown on traces 174,184, 204, and 214. In this data, the pacemaker was not connected to thesubject. Laser outputs are shown in traces 176, 186, 206, and 216. Lasershutter is shown in traces 178, 188, 208, and 218.

Laser output is performed using a laser such as a C0₂ laser, an excimerlaser, or a holmium laser. Other lasers may also be used. The holmiumlaser is a solid state laser requiring some settle down time. In orderto allow the holmium laser to settle down three or four laser pulses ofthe holmium laser are fired but are not delivered to the patient. Thesepulses are shuttered from the catheter 150 using the shutter 132 ascontrolled by shutter control code 142. Not all lasers require thesettle down time and thus not all lasers require a shutter.

In one embodiment, the heart rate is determined, and the time betweenoutputs is set to be about five outputs faster per minute than the heartbeat rate that is determined before revascularization. Two laser pulsesmay be delivered to the patient per laser output. It is desirable todeliver somewhere in the range of one to five laser pulses per laseroutput. The number of laser pulses delivered per laser output may belimited by the number of laser pulses that may cause the heart to beatagain prior to repolarization. The rate of laser outputs may be limitedby the maximum acceptable heart rate for the patient as corrected forthe patient's age. Also, the length of the output should not greatlyinfringe upon the rest time between laser outputs. The number of pulsesper output is variable and selectable depending upon laser parameters,desired tissue effect, and preventing the heart from beating faster thanits optimally acceptable rate. In another embodiment, the rate of laseroutputs per time period is set to ten outputs faster per minute than theheart beat rate that is determined before revascularization. In yetanother embodiment, the rate of laser outputs per time period is set totwenty outputs faster per minute than the heart beat rate that isdetermined before revascularization. In another embodiment the rate ofpacing by a pacemaker or by laser outputs may be slightly slower thanthe heartbeat rate before revascularization.

Prior to revascularization, the pacemaker can be used to synchronize theheartbeat with the pattern that laser outputs will have. Between one andthree laser pulses may be used before revascularization to synchronizethe heartbeat. During laser revascularization, the pacemaker can be shutoff as laser outputs are delivered to the patient. Thus the laser can beused to pace the heart. Upon completion of delivery of laser outputs,the pacemaker may again resume pacing the heart to restore normalrhythm. Between one and three pacemaker pulses can be used to pace theheart after completion of laser revascularization. As revascularizationis performed, the operator maintains a steady but low level of pushforce on the fiber optic, in order to avoid possible increased risk ofunsustained or sustained arrhythmia's from excessive force on the fiberoptic.

A laser output can include a spacing of laser pulses or continuous laserenergy output within a single laser output to cause potentially only oneheart beat in response. The laser energy can be delivered toapproximately simulate the normal rhythm of the heart. A selectablenumber of pulses is provided with the pulses close together in an outputand the interval between each pulse within an output is short enoughsuch that the total time per output is short relative to a single heartcycle. The time between outputs is also variable and selected based upona patient's heart rate. The variable time between outputs generally isset to provide the next output at a time which is slightly faster thanthe patient's resting heart rate, for example at a time which isapproximately five beats per minute faster than the patient's restingheart rate, before revascularization. A laser energy output pattern setclose to a normal heart rhythm pattern may result in capture of theheart rate by the laser thereby allowing the laser to pace the heart.Such a capture may not necessarily occur, in which case an ECG tracingmay illustrate two heart beats, not one during a cycle in which normallyone heart beat would occur. Such a pair of heartbeats is a "couplet."Alternatively, although only one heartbeat per cycle may be visible, twosuperimposed heartbeats may be occurring. Although operating the laserso as to stimulate heartbeats does not require use of a pacemaker, apacemaker may be used to initiate the process. When operated with apacemaker, the pacemaker creates the first beat prior to delivery of anoutput. The sequence is pace, laser output. Use of a pacemaker mayprevent the situation where a pair of heartbeats occurs in each cycle.

FIG. 13 is a flow chart showing a program for revascularization withsensor verify. The program shown in FIG. 13 may be operated on acomputer, implemented in electronics, or may be automated in any otherway, or may be performed by a human operator. If performed by acomputer, the program may be implemented on a personal computer, amicroprocessor, or any other computer, and the program may be stored onany computer readable medium or logic.

A pace signal is delivered to the heart (block 240). The heart beat issensed to determined whether the heart has beat in response to the pacesignal (block 242). If a heart beat is not detected (block 244), thenthe operator is notified (block 246). If a heart is detected (block244), the laser is fired (block 248). Next, the program continues toblock 240. The program senses whether the heart beat has responded tothe pace signal in order to avoid delivering a revascularization eventif the heart has not beat in response to a pace signal.

FIG. 14 is a flow chart showing a program for revascularization withsensor verify and pace rate calculation. The patient's age is receivedfrom the operator (block 260). The patient's heart rate is measuredbefore revascularization (block 262). A pace rate is calculated based onage of the patient and the heart rate before revascularization (block264).

The program waits a period as determined by the pace rate. The period isthe inverse of the pace rate subtracting for time used during thesubsequent steps of the program (block 266). If the footswitch isenabled (block 268), the laser is fired (block 272). If the footswitchis not enabled (block 268), a pace signal is delivered to the heart(block 270). After the laser is fired in block 272, the program proceedsto block 274. After delivering a pace signal to the heart in block 270,the program proceeds to block 274. If a heart beat is not detected(block 274), the operator is notified (block 276). Otherwise, theprogram returns to block 266 to wait for the period determined by thepace rate.

The heart beat may be detected using any type of sensor including butnot limited to an ECG, a pressure sensor, a flow measurement device, oran ultrasound device. An ultrasonic device can monitor, for example,thickness of the myocardium and determine whether a change has occurred.The change in thickness can be correlated with the heart beat. Thus, anultrasonic device can be used to determine whether the heart has beat inresponse to a pace signal and that information can be used totemporarily shut off the revascularization device if the heart does notbeat in response to a pace signal.

The foregoing description of a preferred embodiment of the invention hasbeen presented for purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formsdisclosed. Obviously, many modifications and variations will be apparentto practitioners skilled in this art. It is intended that the scope ofthe invention be defined by the following claim and their equivalents.

What is claimed is:
 1. An apparatus for treating a patient's heart, theapparatus comprising:a catheter; a laser energy source coupled to thecatheter; a shutter positioned to block energy from the laser energysource when the shutter is closed; and a control circuit that isconfigured to close the shutter to block laser energy and to open theshutter to allow the laser energy source to deliver an output of energyto the patient's heart, wherein the control circuit is configured todeliver the output of laser energy over a first time period that issufficiently short so that the output causes no more than one heartheat,and the laser energy source and catheter are adapted to cause heartbeatsby the delivery of the laser energy.
 2. The apparatus of claim 1,wherein the control circuit is configured to deliver the output of laserenergy wherein the first time period is shorter than a second timeperiod from a Q wave to a T wave of the heart.
 3. The apparatus of claim1, wherein the control circuit is configured to deliver a second outputof laser energy after a second time period equal to or shorter than athird time period from a T wave to a Q wave of the heart.
 4. Theapparatus of claim 1, wherein the control circuit is configured todeliver outputs of laser energy at a rate equal to or faster than thepatient's heart rate before revascularization.
 5. The apparatus of claim4, wherein the rate of outputs is 20 outputs per minute faster than thepatient's heart rate before revascularization.
 6. The apparatus of claim1, wherein the control circuit is configured to deliver the output oflaser energy wherein the output of laser energy comprises a set ofpulses of laser energy.
 7. The apparatus of claim 6, wherein the set ofpulses comprises a number of laser pulses in the range 1 to
 4. 8. Theapparatus of claim 6, wherein the control circuit is configured todeliver laser pulses in the set of laser pulses at a rate greater than15 laser pulses per second.
 9. An apparatus for treating a patient'sheart, the apparatus comprising:a catheter, a pacemaker; a laser energysource coupled to the catheter for delivering laser energy to thepatient's heart; a shutter configured to block laser energy from thelaser energy source; and a control circuit coupled to the pacemakerwhich is configured to cause the pacemaker to cause only one heartbeatper the output of laser energy and to control opening and closing of theshutter.
 10. The apparatus of claim 9, wherein the control circuit isconfigured to deliver a pace signal to the heart before causing thelaser energy source to deliver the output of laser energy.
 11. Theapparatus of claim 9, wherein the laser energy source comprises a CO₂laser.
 12. The apparatus of claim 7, wherein the control circuit isconfigured to deliver between two and four pace signals to the heartbefore causing the laser energy source to deliver the output of laserenergy.
 13. The apparatus of claim 9, wherein the control circuit isconfigured to deliver a pace signal to the heart after causing the laserenergy source to deliver the output of laser energy.
 14. The apparatusof claim 3, wherein the control circuit is configured to deliver betweentwo and four pace signals to the heart after causing the laser energysource to deliver the output of laser energy.
 15. The apparatus of claim13, wherein the control circuit is configured to deliver the output oflaser energy over a first time period that is shorter than a second timeperiod from a Q wave to a T wave of the heart and wherein the controlcircuit is configured to deliver a second output of laser energy after athird time period shorter than a fourth time period from a T wave to a Qwave of the heart.
 16. The apparatus of claim 9, wherein the laserenergy source comprises a medical laser having a wavelength in the rangeof 308 nanometers to 10.6 micrometers.
 17. The apparatus of claim 9,wherein the laser energy source comprises a holmium laser.
 18. Theapparatus of claim 10, wherein the control circuit is configured todeliver the output of laser energy the first time period that is shorterthan a second time period from a Q wave to a T wave of the heart andwherein the control circuit is configured to deliver a second output oflaser energy after a third time period shorter than a fourth time periodfrom a T wave to a Q wave of the heart.
 19. The apparatus of claim 9,wherein the laser energy source comprises an excimer laser.
 20. A methodof treating a heart, the method comprising:providing a laser energysource; introducing a laser energy delivery device coupled to the laserenergy source to the heart; using the laser energy delivery device todeliver energy source to the heart cause a revascularization event inthe heart; and causing the laser energy delivery device to deliver fromthe laser energy source an output of laser energy sufficient to causeonly one heartbeat per the output of laser energy.
 21. The method ofclaim 20 comprising:delivering the output of laser energy for a firsttime period shorter than a second time period from a Q wave to a T waveof the heart.
 22. The method of claim 20 comprising:delivering a secondoutput of laser energy after a second time period shorter than a thirdtime period from a T wave to a Q wave of the heart.
 23. The method ofclaim 20 comprising:repeatedly delivering outputs of laser energy at arate faster than the patient's heart rate before revascularization. 24.The method of claim 23, wherein the rate is faster than the patient'sheart rate before revascularization by fewer than 20 outputs per minute.25. The method of claim 20, wherein the output of laser energy comprisesa set of pulses of laser energy.
 26. The method of claim 20,comprising:introducing a catheter coupled to the laser energy sourceinto the heart in a minimally invasive surgery (MIS) procedure.
 27. Themethod of claim 20 comprising:pacing the heart before delivering theoutput.
 28. The method of claim 20 comprising:pacing the heart afterrepeatedly delivering outputs of laser energy.
 29. An apparatus fortreating a patient's heart, the apparatus comprising:a catheter; a laserenergy source coupled to the catheter; a shutter positioned to blockenergy from the laser energy source when the shutter is closed; and acontrol circuit that is configured to close the shutter to block laserenergy and to open the shutter to allow the laser energy source todeliver an output of energy to the patient's heart, wherein the controlcircuit is configured to deliver the output of laser energy over a firsttime period wherein the output of laser energy is sufficient to causeone heartbeat, and the laser energy source and catheter are adapted tocause heartbeats by the delivery of the laser energy.
 30. The apparatusof claim 29, wherein the control circuit is configured to deliver theoutput of laser energy wherein the first time period is shorter than asecond time period from a Q wave to a T wave of the heart.
 31. Theapparatus of claim 29, wherein the control circuit is configured todeliver a second output of laser energy after a second time period equalto or shorter than a third time period from a T wave to a Q wave of theheart.
 32. The apparatus of claim 29, wherein the control circuit isconfigured to deliver outputs of laser energy at a rate equal to orfaster than the patient's heart rate before revascularization.
 33. Theapparatus of claim 32, wherein the rate of outputs is 20 outputs perminute faster than the patient's heart rate before revascularization.34. The apparatus of claim 29, wherein the control circuit is configuredto deliver the output of laser energy wherein the output of laser energycomprises a set of pulses of laser energy.
 35. The apparatus of claim34, wherein the set of pulses comprises a number of laser pulses in therange 1 to 4.